Frictional servomotor



5 Sheets-Sheet 1 y 1949- c. R. HANNA ET AL FRICTIONAL SERVOMOTOR iledNov. 29, 1947 v WITNESSES: 654

July 19, 1949.

c. R. HANNA ET AL FRICTIONAL SERVOMOTOR 5 SheetsSheet 2 Filed Nov. 29,1947 WITNESSES:

INVENTOR5 Chn for) E Hanna. and 5fafl/eyJM/k/na ATTORN EY y 1949- c. R.HANNA ET AL FRICTIONAL SERVOMOTOR s Sheets-Sheet s o Dual Y ak E T N 3M0 M) Y E W Z fl Y 17 B mm 05 Filed Nov. 29, 1947 WITNESSES:

Patented July 19, 1949 FRICTIONAL SERVOMOTOR Clinton R. Hanna andStanley J. Mikina, Pittsburgh, Pa., assignors to Westinghouse ElectricCorporation, East Pittsburgh, Pa., a corporation of PennsylvaniaApplication November 29, 1947, Serial No. 788,866

6 Claims.

/ Our invention relates to frictional mechanisms which transform rotarymotion into translational motion of controllable velocity, acceleration,or extent of travel for positioning, regulating and the like controlpurposes or for the purpose of power transmission or propulsion. Suchmechanisms are disclosed in Patent No. 2,428,807 and in the copendingpatent application Serial No. 788,346, filed November 28, 1947, nowPatent No. 2,473,896, June 21, 1949; and the present invention consistsessentially in improvements relating to mechanisms as dealt with inthose previous disclosures.

' In such mechanisms, an elongated rotor, revolving about its geometricaxis preferably at constant speed, is frictionally engaged by a rollerwhich is mounted on a movable carrier to impart translational movementto the carrier when the roller axis is turned out of parallelism withthe generatrix of the rotor; and a control device serves to turn theroller axis back to the parallel position as the carrier advances alongits path of travel.

3 It is an object of our invention to devise frictional translatingmechanisms or servomotors of the above-mentioned type that permitproviding desired laws of speed or acceleration of the translationalmotion so that the law governing the forward motion is not necessarilyfixed by that of the return motion.

Another object of the invention is to provide mechanisms of the typereferred to which are self-controlled as regards the reversal of thetranslational movement so that only one control impulse, applied from anextraneous source,

is necessary to start the translational stroke in one direction while atthe end of the stroke the mechanism operates automatically, i. e.,without requiring another control action from an extraneous source, toperform a return stroke.

Another object of our invention is to provide mechanisms which areself-controlled as regards operation in both directions of translationaltravel so that the travelling member shuttles back and forth withoutrequiring the application of extraneously governed control or releaseimpulses. In order to achieve these objects and in accordance with ourinvention, we provide the pivot structure of the friction roller with acrank or the like follower member alternately engaged by two cam faceswhich extend along the path of translational travel, and we control theangular movement of the roller pivot during the forward and returnstrokes respectively, by two control members, located near therespective ends of translational travel, which switch the followermember from one to the other cam surface.

These and other objects and features of the invention will be apparentfrom the embodiment illustrated in the drawing.

The illustrated servo mechanism is designed as a drive for the flyshuttle of a weaving loom. Fig. 1 shows a part-sectional View in theaxial direction of the driving rotor, Fig. 2 a view taken from theright-hand side of Fig. 1, and Fig. 3 a top view relative to Fig. 1.Fig. 4 is a sectional view of carriage and friction roller, and Fig. 5shows the control device for turning the pivot of the friction roller.

- In the drawings, numeral l denotes a composite stationary frame orsupporting structure. A rotor 2 of elongated cylindrical shape isrevolvably mounted in bearing plates 3 of the frame structure. The shaft4 of rotor 2 is connected to an electric drive motor (not shown)operating substantially at constant speed. The rotor 2 is maintained incontinuous revolution during the operating period of the weaving loom.-Held against the cylindrical surface of the rotor is a friction roller5. Roller 5 is mounted on a ball bearing 6 whose hub portion is seatedon a; hollow shaft 1 (Fig. 4). As shown, the roller 5 consists of theouter race member of the ball hearing which has a normal design, exceptthat its outer surface is ground to a slight curvature to reduce theStarting torque required to tilt the roller. The roller shaft 1 isattached to a fork-shaped supporting member 8. Integral with this member is a pivot shaft 9. The axis of pivot shaft 9 extends at a rightangle to the geometrical axis of rotor member 2. The axis of revolutionof the roller 5, i. e., the geometrical axis of hollow shaft 1, extendsat a right angle to the axis of pivot shaft 9.

Shaft 9 is journalled in a thrust bearing l0. Bearing l9 rests against acarriage structure ll equipped with four ball-bearing wheels, alldenoted by l2. The wheels engage two rails I 3 and I4 that are firmlyattached to the frame structure I and extend along the rotor 2 inparallel to the rotor axis. The frame structure has a weakened orhinge-like portion, at [5 (Fig. 1), capable of permitting movement ofbearing plates 3 and rotor 2 toward the carriage structure. Two helicalcompression springs ["6 and I! secure the necessary frictionalengagement between rotor 2 and roller 5 while forcing the carriagewheels against the rails 13 and I4. Springs l5 and I1 are disposed onthreaded bolts 18 and I9, respectively. The bolts are anchored in ashuttle box structure 20 that is mounted on the frame structure to form.a rigid part thereof. One end of each spring rests against a bracket 2!of the appertaining rotor bearing plate 3. The other. spring end abutsagainst an adjusting unit seated on bolt t8-or I3. The machined hingeportion E5, as shown, is. preferably located. at the. base of a verticalline (Fig. 1) through the point of application of the spring force onthe shuttle box 20 and the point of contact of roller with rotor 2.

It will be recognized that the springs I 6 and I1, as compared with thebiasingmechanismsdis-- closed in the above-mentioned patent are notdisposed on the carriage It sothat; the carriage:

structure can be given a greatly simplified design of considerablyreduced. weight or mass. As-

a further result, the spring force can readily be adjusted withoutrequiring a removal ordisassembly of the carriage.

-.Attaehedto the carriage structure Ll. is a member zznthatcarries a"metal cup 23.: for engaging the fly shuttlev 2 l to be propelled by themechanism. The cup- 23 also serves tobringr the shuttletoiastop on-itsreturn from the other side of the loom. The returning. shuttle is brakedwhen it; enters. the shuttle box by wedgingitself between.spr-ing-backed friction shoes 2:5, 26 (Fig. 1.) extending the length ofthe shuttle box 20. Cup-23 is filled with rawhide. or other suit.-

able; resilient material to be engaged by the steel-tipped-vnose'of theshuttle.

When the axis. of revolution of friction" roller iis in. the illustratedposition of parallelism with the generatrix of rotor 2, the. revolutionof the rotor has merely theeifect of revolving the roller 5' imparts nodriving force. to the carriage structure Ll. -Wherr shaft 9 is turned,thereby twisting. the roller axis relative to the generatri-x of rotor2,. the carriage assembly'is propelled along the rails atavelocitysubstantial-ly equal to the. peripheral velocity'of the. rotortimes the tangent of the angle throughwhich shaft. 9 has turned. Inorder to impart.- hightranslational acceleration to-the carriage orshuttle, for-in,- stance in the order of 100v times gravity, theangular. adjustments of; the shaft 9- must be accuratelycontrolledwithin short intervals of time. For example, in a'specific loom shuttledrive-, the shuttle: is: uniformly broughtup to. a. speed of feet, persecond within about second at .the end. of 6 inches of travel. 7 From.this poi-nt on, the carriage; begins a uniform deceleration that 4' 7are engaged by the roller 28 during the forward and return travelrespectively of the carriage. The two slots communicate with each other,at

both ends so as to form a continuous guiding engaging the member 33 andattached to the plate 29, biases the switch member 33 toward engagementwith a stationary stop 33'.

A similar switch. member-warmth a control surface 31 is pivoted at 35anear-the other end of the cam slots and is; biased bye; spring 36atoward engagement with; a stati'onary stop 36. r

The crank arm 21 forms a nose at 40 (Fig. 2)

for engagement with a latch 4| which is pivoted at M on the framestructure I and linked to a magnetic core member 43 by means of an anglemember- 44 (rEigsa; 2-and 3 A; solenoid coil- 45, mountedon a-v magneticfield structure: 46:; serves to control the eon-Hi5 so thatwhen thecoil: 4-5-is energized,v the: latch; 44: is released from% th-esnose 48of crank arm 21.

The'upper groove or. slot.3.t controls; thecarriagemotion" in. theforward direction, e:,, from left toright. in Fig; 5 The shape ofgroove3! as illustrated-i in.Fig;. 5. is calculated. tmimpartz'a; constantacceleration to the-carriage during'therflrst half. of the. forwardtravel,;followed by; a. constant deceleration of the'carriage inthezsecondvhalft ot the forward stroke. V p

,Whenthe carriage comes'elose. to; the: end? of its forward stroke. theroller; 28: beginsto engage the. control; surface 31: oi switch.-memberr3w3m-aml moves this member. elockwisein opposition to:- thebrings it to-a stopinv another .6- inches of travel, 7

while: the shuttle travels under its own-momentum to the. otherside'oftheloom. The means for securinga control; of this kind will bedescribed presently.v

The pivot shaft 9 carries an. arm or the like crank member 21 whoseactuating end is equipped with. aroller- 2th to. engage the cam facesof: a cam. device (Figs. 1, 3, .4, 5)... The cam device has a cam. plate29 firmly. secured to the frame structure L and has two grooved slotswhich extend along. the rotor 2. and. along the path of travel ofcarriage ll. While the cam plate may consist of a. single. piece, theone shown. in. the embodimentv has a separate center piece 29' firmlyattached to the outer part of plate 29 by means of two. bridgingpiecesof which one is shown in Fig. 5- at 3i while the other, in the samefigure,.is. assumed tobe removed in order. toex pose.- other parts of.the mechanism. The edges of the. upper cam slot 3|. and the edges of thelower slot. 32' (Fig. 5) form the: cam faces-which.

biasing spring 36w; Due-to the actions of the spring,. the member 33a.-forces the roller 23 downward intoengagementwith the; lowercam slot 32whose function. it. istcr. control the, carriage. motion during thereturnparti'ofi itscyele; The carriage can be returned to its startingpoint at; a. reduced velocity,-. if: desired. depending: upon the.selected. shape anddi-spositiomofrthe lower cam slot. I V

When-the. carriage. is olosev to; the: end-of its return: stroke, the.roller 2:85 engages: the cami surfaceeo-f. switching -member33 and movesit down:- ward against the force of the biasing spring 13% Thus. at theend. of the: return; strokehwheirr the arm 21' is again horizontalandithe: carriage-astertionary, the switch; member 33 is exertingantip-v ward force. However, they armv I24 lockedin this. horizontalposition; by the latch 41; .whiclic'is spring. biased. toward the arm?!(Fig.2); m

sequently, thearm: 21- remains in; horizontal posittionin which thefriction roller 5-has the: position shown in, Figs- 1, B -andv 4: sothat thercarriage remainsat restin theillustrated positiom. When the.instant tor propulsion of the shuttle'isreached in the operatingcycle-of the weavingloom, the

latch M is pulled away the arm 2:1 an

electric: impulse transmitted by, somesuitable control circuit (not.illustrateda to; the solenoid 45, The spring-biasedswitchmember 33 isthen device corresponding to the elements 40 through 46 may also bedisposed near the other end of the translational travel so that both theforward stroke and the return stroke are to be initiated by controlimpulses depending upon the operating cycle of the associated machinery.On the other hand, the latching device may be omitted, orv the latch 4|may be held in disengaged position so that then the mechanism iscompletely selfcontrolled to continuously reciprocate its carriage. Itwill be understood that if latching devices are employed, these devicesmay be operated by other than electromagnetic means, for instance, by amechanical transmission or by a hydraulic control system.

' Although the frictional servomotor specifically described in theforegoing and shown in .the drawings is designed as a shuttle drive forweaving looms, it is apparent that the invention can likewise beembodied in mechanisms for other purposes, such as the propulsion orcontrol of torpedoes, aircraft, gun control systems, and, in general, inservo-mechanisms for which an aperiodic or non-oscillatory response isdesirable.

It should also be understood that while I have illustrated andspecifically described a mechanism whose driving rotor is cylindrical,the rotor may be given conical shape or generally the shape of a body ofrevolution. It will be obvious to those skilled in the art upon study ofthis disclosure that the invention permits various modifications,embodiments, and applications, other than those specifically mentioned,within the gist and principles of my invention and without departurefrom the essential features of the invention set forth in the claimsannexed hereto.

We claim as our invention:

1. A device for deriving translational motion from a source of rotarypower, comprising a rotor revolvable about its geometric axis, astructure movable along said rotor, a pivot revolvably mounted on saidstructure, a roller in frictional engagement with said rotor andrevolvably mounted on said pivot so that the axis of roller revolutionextends at a right angle to the axis of said pivot, a cam followermember attached to said pivot for turning said pivot, control meansdisposed for causing said follower member to turn said pivot shaft andhaving two cam faces extending along the path of travel of saidstructure and engageable by said follower member during the forward andreturn strokes respectively, and two switching members disposed near therespective ends of said path of travel for switching said followermember from one to the other cam surface.

2. A device for deriving translational motion from a source of rotarypower, comprising a rotor shaped as a body of revolution with asubstantially straight generatrix and being revolvable about itsgeometric axis, a structure movable along said rotor, a pivotjournalled. on said structure to be revolvable about a pivot axisextending substantially at a right angle to said generatrix, a frictionroller revolvably mounted on said pivot about a roller axis extending ata right angle to said pivot axis, said roller being in frictionalengagement with said rotor, a crank member on said pivot for turnin thelatter, a cam device having two mutually spaced and substantiallyco-extensive slots engageable by said crank member during the forwardand return travel respectively of said structure, said slots extendingalong the path of travel and communicating with each other at therespective ends of said path, and two switching members mounted nearsaid respective ends and engageable with said crank member for switchingit from one to the other slot;

3. A device for deriving translational motion from a source of rotarypower, comprising a stationary supporting frame, a rotor revolvableabout its geometrical axis relative to said frame, a structure guided onsaid frame for motion along said rotor, a pivot member revolvablymounted on said structure, a friction roller revolvably mounted on saidsupport pivot member and in frictional engagement with said rotor, a camfollower member on said pivot member for turning said pivot member tocontrol the angular position of the axis of said roller relative to thegeneratrix of said rotor, a cam device mounted on said frame and havingtwo mutually spaced cam faces extending along said rotor, said followermember being engageable with said cam face during the forward and returnstrokes of said structure respectively for progessively turning saidpivot member as said structure travels along said rotor, two switchingmembers mounted on said cam device near the respective ends of said camfaces and being spring biased and engageable with said follower memberfor switching the latter from one to the other cam face, andcontrollable latching means associated with one of said switchingmembers for latching it in a position where it holds said followermember so that said roller axis is parallel to said generatr-ix.

4. A device for deriving controlled translational motion from a sourceof rotary power, comprising a stationary supporting frame, an elongatedrotor revolvable relative to said frame, a structure guided on saidframe for motion along said rotor, a pivot member mounted on saidsupport and being revolvable relative thereto, a friction roller mountedon said pivot member for revolution about an axis at a right angle tothat of said pivot member, said roller being in frictional engagementwith said rotor and having a cam follower member for turning the axis ofsaid roller at an angle to the direction of the generatrix of said rotorin order to cause said structure to move along said rotor, a cam devicehaving two cam slots extendin along said rotor and engageable by saidfollower member in all travelling positions of said structure, saidslots communicating with each other at their respective ends, twoswitching members pivoted on said cam device near the respective ends ofsaid slots and having respective control surfaces, spring means forbiasing said respective members so as to have said control surfacesproject into the path of said follower member in order to throw saidfollower member from one to the other slot as it impinges upon saidrespective switching members.

5. A shuttle drive, comprising an elongated cylindric rotor revolvableabout its cylinder axis, a wheeled carriage movable along said rotor inparallel to said axis and having shuttle engaging means for impartingmotion to the shuttle to be driven, a pivot member mounted on saidcarriage so as to be revolvable relative thereto, a friction rollerrevolvably mounted on said pivot member and in frictional engagementwith the cylindrlc surface of said rotor, a cam follower forming part ofsaid pivot member for turning it relative to said structure in order tocontrol the angular position of the roller relative to said cylinderaxis so that, during revolution of said rotor, said structure remains atrest when said roller axis is in parallel to said cylinder axis and iscaused to move alongsaid drive member whensa-id roller. axisis placed;at an angle to-sa-idcylinder axis,- a cam device having two mutuallyspaced cam faces ex.- tending along said rotorrandengaging said camfollower inall travelling positions'of said carriage, and-two switchingmeans. mounted on said cam devieenear the respective ends-of saidcoextensive slots,- said switching means; projecting into the; path oftravel of said cam follower for transfer ring said follower from one to.the other cam face. i

-6'.- A- shuttle drive, comprising an elongated cylindric rotorrevolvable about its cylinder axis,- a wheeled carriage movable alongsaid rotor inparallel to said axis and-having shuttle. engaging; meansfor imparting motion to the shuttle to be driven, a pivot member mountedon said carriage;

so as to be revolvablerelative thereto, a, friction roller re'volvablymounted on said pivot member and in frictional engagement :with-thecylindricsurfaceof said rotor, a cam follower forming part of saidpi-vot member for turning it relative to said structure in order tocontrol the angular position of the roller relative to saidcylinder axisdevice having two mutually-spaced: oam faces extending; along said,rotor and engaging sa-idi eaifi follower in all travelling positionsoft, saidlcanriage; twoiswit'ching members pivoted- 011a saidcam:

device near the IESPGCtiVGrflIIdS of: saidi slotsaan'd having a control;surface; spring means disposed? between said cam device and saidrespective switching members for, biasinga-said: switching: member-so:that said. control surfaces project. i-ntoithe path; of; said followerin=:order' to throvv: it; from one to the other cam 'face' -w-li'en.said carriagereaches; either end ofiitsitravel, a'latciie mg deviceengageabl'eWJitIi-oHe of said switching members for hol'ding itiinposition to. arrestasai'cfr carriage, and electromagnetic. controlmeans? associated with said latching device for releasing said oneswitching member; e 1

- .o 1 CLINTON R. STANLEY J. MIKINA;

- REFERENCES CITED 7 n The following references are of record in} me ofthis patent:

' STATES PATENTS,

Number Name Date 2,215,678 Weathers Sept. 24; 1940 12,382,105 SarverAug. 14,1945?

